So how do you find the best auto finance rate? The first place to start is Bankrate's daily update of loan rates . These are averages and will give you a starting point to determine what's high or low when it comes to APR (annual percentage rate), the best yardstick for loan comparisons.

But loans vary greatly, depending on the lender, your credit and regional factors. The tool above will help you compare car-loan rates in your area, and then see if you can do better. Most banks and credit unions offer online auto loan quotes and applications. Then there are online lenders like E-Loan and Capital One Auto Finance which have been offering highly competitive rates.

It's best if you get about three different loan quotes. If one seems especially low, verify that it's an actual offer to lend you money at that price and not just a gimmick to get you signed up before the real numbers appear, or you find out that the credit requirements are impossible to satisfy.

Aside from the usual requirement for great credit, there are ways in which zero-percent car loans can trip up a buyer. Most interest-free financing offers require financing terms of three years or fewer. So you'll have to pay large monthly payments if you qualify.

Let's say you're borrowing $20,000 to pay for your new car. With a three-year term at zero percent interest, your family would have to pay more than $555 a month in car payments. A five-year term at 3.9 percent with monthly payments of $367.43 may be more manageable, even though you have to pay some interest.

Also, some zero-percent offers require you to put down as much as 25 percent, whereas most other finance deals require as little as 10 percent or even nothing down.